Drafting instrument



Oct. 13; 1959 G.

s. DOLGORUKOV 2,908,082

DRAFTING INSTRUMENT 3 Sheets-Sheet 1 Oct. 13, 1959 s. s. DQLGORUKOV 2,908,082

' DRAFTING INSTRUMENT Original Filed April 26, 1946 3 Sheets-Sheet .2

Oct. 13, 1959 e. s. DOLGORUKOV 2,903,082

DRAF TING INSTRUMENT Original Filed April 26, 1946 3 Sheets-Sheet tug-w DRAFTING Gregory S. Dolgorukov, Ferndale, Mich. I

Continuation of application Serial No. 665,186, April 26, This application August 28, 1953, Serial No. 7 82 j '2 Claims. (Cl. 33-110) This invention relates to drafting instruments and more particularly to an improved drafting device or template of universal utility in drafting work, and particularly a. device enabling the'draftsman to do rapidly and easily most of the straight line operations encountered inave'rage drafting work, including .section lining. 1

I The present application is a continuation of my aban-J. cloned application Serial No. 665,186 filed April26, .1946;

for Drafting Instrument. In preparation of mechanical drawings, i.e. drawings made with the aid of instruments as distinguished from free hand sketches, the major portion of the work is devoted to drawing straight lines. These are made by drawing the point of a line-drawing instrument, pen or pencil, along a guiding edge. Most of the lines appearing on an average drawing are either parallel to the base line of the drawing, perpendicular to it, or are inclined at 30, 45, or 60 to said line. Lines parallel to the base line of the drawing, are usually drawn against the edge of a T-squa-re. As to lines disposed .at various angles to the base line, they can be drawn only after their.

proper angular relation to the edge of the T-squa-re is first established. Since measuring the angle each time when such a line is to be drawn is along and tedious pro-.

cedure, angular templates are used for drawing lines at angles most frequently occurring. While it is desirable .to draw lines at as many angles as possible without measuring the angles, it is equally desirable to have as few templates or special devices as possible. These conflicting requirements have presented a problem or established the need of a single'device enabling the draftsman to draw with its aid as many angular lines as possible.

Answering the need or problem present in the art, numerous devices aiming to provide for drawing lines at various angles to the base line of the drawing or the edge of the T-square have been offered. One of such devices,

known in the art under the name of fdrafting machine is still a very complicated and expensive device, and is outside of the reach'of many draftsmen, and particularly students. Other devices madefor the same general purposes are usually in the form of various polygons having sides disposed at a number of angles to the base line.

These devices, although enabling drawing lines at many angles, have a serious disadvantage of being too large, heavy, and cumbersome to use. Moreover, they require somewhat diiferent habits of handling than those acquired by draftsmen since their school days and through years of practicalwork in using common triangles. Therefore, although used occasionally, such devices have not received universal application, and a draftsman or a student of drafting usually depends on two triangles for drawing angular lines, namely, one right-angled triangle with two 45 angles, and another, also a right-angled triangle but having 30 and 60 angles, sometimes using them in combination with each other, but usually changing from one to the other.

A large number of angular lines on'a drawing is usual 1y drawn also in the process of section lining i.e. cov

I 2 ering the surfaces presumedto be cut or broken away to 'e'ir'pose the interior, with fine parallel lines usually inclined at 45 to the baseline, closely and uniformly spaced to give the section lined surface an even shade or appearance; Section lining is usually done with the aid of a 1 45 triangle, spacing of the triangle in steps being done by eye.

It is well appreciated in the art that of all, drafting V operations section lining is not only a most tedious but also one of the most strenuous and injurious for the draftsmans eyes. This is partly due to the fact that in section lining with a draftsmans triangle, setting it for each successive line by eye, one must s'et'the nearly transparent edge of the triangle at an exact distance from a fine, hard-to-see line. Although through years of ex- 7, perience a draftsman may develop a finger control enabling himto'do relatively rapid section lining by: eye, he

continues to strain his eyes and often thus to tax heavily his "eyesight. 'Since in sectionlining the draftsmen must keep in the'shaip focus'of his'vision an area covered with uniformly spaced lines, many usually unnoticed eye defects, such 'as blind spots on the eye screen, become pain fullyevid'ent much sooner than they normally would and produce'severe headaches, nervousness and fatigue. In

fact, the realization of the necessity of retiring from draw ing board work often comes to a draftsman by way of hisr'ealization of the inability to continue doing section lining, which o'pera'tion'is necessary in the preparation of nearly every mechanical drawing. In view of the above,

if -the'eye strain incidental to sectionlining is eliminated, many ari'old skillful 'draftsman could continue his'drawingboardwork for several years longer, and many an older technician who usually refrains from making even occasional drawings because of failing eyesight, could do such work occasionally without the fear of discomfort or-paiii. I V

Much inventive effort has been directed throughout many years to devising a practical section lining device convenient for use in routine drafting and designing work on the drawing board. However, in spite of a large number ofdevices ofl'ered, none of them attained universal application, and section lining in industrial drafting rooms is still done almost universally by eye and is so taught in schools. This is due primarily to the fact that conventional section lining devices are usually in the form of rulers movable in steps by some sort of manually operated mechanism. Such devices are notonly' complicated and costlybut are rather difficult to set up. 1 Some of them,

for instance, have to be set on needle points and moved around the drawing, piercing it in numerous places as the workprogresses. Some of such devices cannot be used close to the edge of the drawing board and therefore are very diflicult'to use on small boards such as are used in schools. Therefore, such devices are usually regarded, particularly by educators, as being only of occasional value in special cases but not worth the trouble of setting up foryordinary work, which makes it undesirable for students to become dependent upon them.

- Many 'draftsmen do section lining by putting a coin or a small block of wood into the central opening of'an ordinary triangle. Spacing in. steps is effected by hold ing the triangle and-moving the coin and then holding the coinand moving the triangle. However, since central openingsin triangles are not cut, in any particular re-' lation to the size of coins, the spacing so produced seldom has a desired pitc or distance between the section lines,

" the same being usually so wide as to be impractical.

Moreover a single spacing or a spacing produced with the same triangle using dilferent coins does not satisfy the requirement usually met in the preparation of a drawing where using several pitches for indicating diiferent parts or materials is necessary.

Patented Oct. 13, 1959 in their use.

Many attempts have also been made to incorporate into 7 the central opening of a triangle some sort of a mechanism permitting an adjustment of the section lining. Such expedients, although performing the function intended, proved to have a vcry serious disadvantage preventing theirwider application It can be easily appreciatedthat sucha device; although including a triangle, becomes for all practical purposes exclusively a se ction lining device and loses most of its convenience in use as a drafting triangle. This is due particularly to its increased weight and interference of its spacing mechanism with such handling of the triangle as the draftsman became accustomed to through years of work and which he tends to ,follow unconsciously. Occupying additional space on the drawingboard, such a triangle has to be put away after each use and taken out every time it is needed. .Thus, these de- Vices aIthough generally less expensive than mechanically spaced rulers, have substantially the same disadvantages One of the objects of the present invention is to pron vide' a drafting instrument or a template which enables the draftsrnan to make most of the straight lineconstructions and drawlines at most of the usually required angles,

' pa t eqla ly insm l e r u as t i n w t one instrument only, and moreover to do rapidly and,

easily uniform and neat section lining in a large number of spacing pitches without the necessity of procuring and handling a special section lining device, and thus to. facilitate drafting work, save time and decrease the number of drafting instruments required on the drawing board;

usually already too crowded with instruments.

Another object of the invention is to provide an improved drafting instrument or a template of the character vide an improved center piece for a drafting triangle having a central opening of predetermined dimensions,

which piece provides for four. and more spacing pitches of the section lining.

A still further object of the present. invention is to provide an improved section lining device including a triangle havinga central opening, and a center piece placeable therein a number of operative positions, which center piece is of such an outline and proportions .as to slide easily and bear firmly on the edges of the triangle without rocking, in all such positions, and does not require the provision of special guiding or steadying means for its operation.

A still further object of the present invention is to provide a center piece for a section lining triangle constructed in a manner to produce a piece giving a large number of predetermined spacing -pitches, and thus to eliminateguessing and extremely long drawn out and try methods. I

A still further object of the present invention is to proing of such a character as not only to accommodatejthe center piece in a predetermined manner but also to provideinstmment-guiding edges fordrawing lines at angles to the base line unattainable with the outside edges of the triangle.

A still further object of the present invention is to provide a drafting triangle of the character specified in' the preceding paragraph, which can be converted in a few specified in the preceding paragraph, which is lightand:

requires the same handling habits as a common triangle:

Astill further object of the present invention is to provide an i mprovedsection lining device which enables the draftsrnan to, dosection lining withoutdependence on thev eyes and yet to produce uniform and neat section. lining.

A stillfurther object of the invention is to provide, an

improved section lining device which makes section; lining. in easyand rapid operation. A still further object of. the invention is to provide an;

a common drafting triangle but which 1 does not .connect.

any. parts to, thetriangle or changes said. triangle appreciablyffromits accustomed shape, thereby enabling the specification, wherein like reference characters designate I draftsman to use said triangle for all drafting work in:

exactly the same manner as if it were a conventiona triangle, and without changing. his. habits.

A still further object of the present invention is to pro-. vide an improvedsection lining device Without adding, as

far as expenses and the room on the drawing boardare concerned, any new instruments but by utilizing a triangle, and'by. adding only a small center piece placeable without any interlock or mechanical connection into the central opening of the triangle and removable therefrom used for all drafting work as a conventional triangle and.

be, convertedinto a section lining. device in a matter of less than a second.

A still further object of the present invention is to pro,-

. andlthecenter piece to provide a number of additional 7 seconds andwithout being put aside into a section lining device'of a desired spacing pitch, and reconverted into a customary draftingtriangle just as simply and quickly.

vIt is'an. added object of the present invention to provide a drafting instrument of the foregoing character, which is simple in construction, convenient in use, and inexpensive; to manufacture. V .O=the r objects of'this invention will appear in the following description and appended claims, reference being had tothe accompanying drawings forming a part of this corresponding parts in the several views. I

'Fig. 1 is a view illustrating a drafting instrumentembod'yingthe present invention, the instrument .being arranged on a drawing board against a T.-square and set for section lining at 45 and to. the base line in a spacing pitch produceable with the corner edge designated by thenumeral 1.

Fig- 2 isa view similar in part to Fig. l, the instrument beignturned over to have the 45 section lines running inltheother. direction, i.e. at to the baseline.

Fig.1 3 is aview illustrating the instrument setfor useasadrafting triangle and showing the various angles and angular lines obtainable therewith.

. Eigs A-JO, inclusive, illustrate the relative positions of the. triangle on the T-square and of the center piece in the opening of triangle for section lining in spacing pitches 2-8, respectively.

Fig..11 illustrates additional portions of thetriangle spacing pitches.

Figj. 12 shows thecen ter piece separately.

13 is anend view ofthe center piece, the observer beingpresumed to look from the right. i

[ Fig. 14 shows the-pencil guiding edge of the triangle in section and on an enlarged scale, thethickness of the trlianglebeing sornewhat exaggerated as compared with thesiz e'. of .the pencilfor the sake of. clarity.

f l3 e forel explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details-of construetion and arrangee t eti ts il us a e e aqs m s draw n since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation, and it is not intendedrto limit the invention claimed herein beyond the requirements of the prior In the drawings there is shown/by way of example an improved drafting instrument embodying the present inking pen, a scriber and the like may be used. Therefore the term pencil guiding edge should be understood as a line-drawing instrument guiding edge. The term base line as herein used refers to the line at the bottom of the drawing, parallel to the straight edge of the. T-

square.

Referring to the drawings, the instrument or device illustrated therein comprises a triangle, generally indicated by the letter A, and a separate center piece, indicated by the letter B. The center piece B is selectively insertable into the central opening 20 of the triangle, A to fit therein any of the several operative positions, and is removable therefrom.

The triangle A has the outline or outside shape of a conventional 45 drafting triangle and is used in all drafting operations as such. An important feature of the invention is the provision in said triangle of a special central opening. In conventional trianglessuch openings are provided for the purpose of removing some material and to facilitate picking the triangle up. In my improved triangle the central opening is of such a character as to resemble the conventional triangle openings to. which an average draftsman has been accustomed as far as handling the triangle is concerned, and yet to provide additional pencil guiding edges enabling the draftsman to draw with my improved 45 triangle lines for which formerly he would have to put aside his 45 triangle and to reach for the 60 triangle. Since indrafting it is constantly necessary to draw lines at variousangles, mostly at 90, 60, 45, and 30 to the base line, constant changing of the conventional triangles, particularly for drawing only short lines is not only annoying but very time consuming. By the use of my improved triangle such chang ing of triangles is greatly reduced, and short lines at 30, 60, 75, 10.5, 120 and 150 to the base line, for which either 3060 triangle or a combination of both 45 and 3060 triangles have been necessary, are positively established with the aid of my triangle-directly from the straight edge. Moreover, many angles, including mutiples of 150 may be measured directly with my triangle, and without the use of a protractor. The above results are attained by providing in the triangle the central opening of the character best shown in Fig. 3. As can be clearly seen from an examination of said figure, the central opening 20 has its inner edges 21a, 22a -and 23a parallel to the outside edges 21, 22 and 23 of the triangle,

respectively, but the 45 angles are closed by edges 24 and 25 running at 15 to the line bisecting the 90 angle. It is desirable to have these edges of substantial length, and it is preferable to make them as long as possible without producing interference, with the corners of the center piece in the positions thereof illustrated in Figs. '9 and 10.

It should be understood that it is preferable to cut the central opening in such a manner. as not to injure the piece which is cut out, since such piece will have the outline similar to that of the central opening and may be used as a drafting template for fine or detailing work, with a number of important advantages.

Further important advantages of my improved triangle result fromthe improved construction of its pencil guiding, edges, shownin Fig. 14. The corners 31 of the edges are: removed in'any suitable mamier, either by chamfering or by rounding the pencil guiding edges, and the edges are polished. This simple expedient results in a' large number of important advantages of my improved drafting instrument over drafting instruments having square edges. It canbe appreciated that with the corners 31 left square, as in conventional triangles, the sharp corners grind into the pencil side, bringing the pencil point closer to the edge, and depositing a layer of carbon on the top of the edge as indicated at 32 in Fig. 14. In section lining, should the pencil be turned in the hand after drawing one section line, the correctly spaced edge will produce smaller spacing of the next section line, thus interfering with the uniformity of section lining. Moreover, when the triangle is turned over as is frequently done in the process of drafting, the carbon deposit 32 although hardly noticeable to the eye while on the edge of the triangle, is smeared over the white drawing paper, producing dirty spots. Erasing such dirty spots'is very diflicult, .since they usually occupy relatively large areas in which many lines are drawn, and extreme care is necessary not to erase or lighten such line while removing such spots. In many cases, such as in design work, the drawing may get unacceptably dirty and since its cleaning is difli cult, as explained, redrawing it may be necessary. With my improved edge, the corners 33 are much blunter, and do not cut so readily into the graphite. This diminishes interference with uniformity of section lining. Moreover, whatever graphite may accumulate along the corner 33 as shown at 34, .will not get on the drawing when the triangle is turned over, since it will remain well above the paper as shown at 34a. The edge can be easily cleaned by drawing it over an eraser, or by wiping it with a piece of paper.

It can also be seen that by lowering the point of con tact of the line-drawing instrument from the corner point 31 to the corner point 33, the undesirable effect of changes in inclination of the pencil on the straightness of the line drawn is greatly decreased in my improved edge. It can be appreciated that as the line is drawn and the arm of the draftsman moves, there may occur a slight change in the inclination of the pencil transversely of the edge. The higher is the point of contact of the pencil with the guiding edge, the greater will be the resulting deviation of the pencil point and the drawn line from the theoretical straight line. Such deviation reduces precision of graphical constructions in the drawings and interferes with the uniformity of section lining. By lowering the point of contact of the pencil with the guiding edge, my improved edge reduces proportionally the above undesirable effects.

It can be appreciated further that removal of the corners 31 also results in lowering of the shadow from the edge, see Fig. 14, which shadow often makes the pencil line invisible and drafting work difiicult. Additional advantages of the above expedient are found in much safer inking, no matter which side of the edge is up, and in more pleasant handling of the triangle. It is well known that square edges are very difiicult to do inking workwith, and that sharpedges makeit very unpleasant to handle the triangle. In addition to the above advantages, by polishing the edge, the dragon .the pencil is eliminated and the pencil is caused to slide along the edge easily and smoothly.

I prefer to make my triangle of a harder. and more transparent material than cellulose nitrate sheet stock or celluloid used for conventional triangles; moreover, I prefer to have the surfaces of my triangle finished in fine dull or satin finish. This finish should be suficiently dull toprevent reflection of shiny or light objects, but fine enough to prevent the surface from getting dirty. Making the triangle from acrylic resin, such as one known glare due to the reflection of overhead lights or windows,

which reflection is common with conventional triangles, is eliminated in my improved triangle, and yet the requisite transparency of the tliai gle is retained. T 6 harder material takes a much finer than. convention l inl terials and is therefore less din-colle tingi It will be understood that the above c nstruc ion, of

section lines. It is important to appreciate that such position of the triangle will not change the spacing pitch of the section lining The same results can also be attained by turning the triangle and the center piece overa unit on the edge-21,- and bringing them into the position shown inijFig. Again, 'the spacing pitch willremain the same.

If vertical lines are desirable, ,the same may be drawn along-the edge 21 as indicated in Fig. 1. It is important the edge is not limited to use in triangles, and" that'it may be used in other instruments havinginstrument-guids. ge

By vir ue of the above con truction, my improved tiriangle forms a v ry useful instr men for g neralfdraafitiug work, and in many instances n t on y talcesplace. or he two conventional triangles, but, due to improved, edges, enables the draftsman to do better work and do it faster and easier} In'addition to the'above important advang y improved tri ngl possesses an addition l. advantage of great importance, namely the capacity of being easily converted into" a sec i n l ning device. in a mat er of one second or so, and reconverted into a drafting tri angle just as speedily and easily.

Such a result is attained by providing; the. trianglc in addition to the central opening of the chafaCtcr described above, also with a loose center piece such as designated y the letter B. Referring to Fig- 1 the center piece B comprises a rectangular piece. of a suitable material; having approximately the same thickness as the triangle. The 90 corners of the piece are slanted at 45 angles for predetermined diiferent distances to produce an octagon with sides of different lengths. These different distances are measured either from the corner points 40 of the rectangle, or from the lines 41. corresponding to edge 23a of the central opening and cuttin the corner'of the rectangle along the lines corresponding to. the. four positions of the'edge 23a, shown in Fig. 12, wherein 1, 2, 3 and 4 equal spaces measured from said, line. are shown removed from the corners' These distances will determine the spacings between the section'lines; oi spacing pitches obtainable with the center piece using the, slanted corners as stops for the triangle.

It can now be seen that if the piece of such an outline is placed within the central opening Qfthe. triangle to appreciate'that drawing lines against the edge 21 will increasethe spacing pitch of said vertical lines to-2 times the spacing pitch of the inclined lines.

Placing the piece into the triangle opening with;its other corner edgesffl', 3, and 4, respectively, against the edge 23a will changethe spacing pitch of the inclined lines to the distance at'which said corners are cut-away from the reference lincs 41'. Figures 4,5, and 6 of the drawings illustrate the relative positions of the center piece for producing such spacings, it being understood that the position of the triangle need not be changed.

With the construction so far explained four spacing pitches are obtainable, and if only four pitches are desirable, the center piece may be laid out as explained above and illustrated in Fig. 12. I have found, however, that four definite spacing pitches do not satisfy the requirements of various types of drafting work for which the same device may be put. For instance, while four spacing pitches ranging, say, from /3 to may be entirely sufficient for small drawings, such as school draw- A, with any of its cut away corner edgesadjacent th hypotenuse edge 23a, of the opening and with ts t o square sides bearing on the sides 21a and 2 a of the opening 20, there will be a clearance between the hypd enuse edge 23a of the opening an the' orner of. he Piece B; whi h clearance is equal to the distance cut aw y from that particular corner over or beyond the line 41. Now, if both the triangle A and the piece, B are firmly held against the paper in such a position and a line is drawn against its outside hypotenuse edge 23, and then the triangle is moved along the T-square until stopped by the piece B held firmly in its position, the'clearance will be eliminated at the corner. If another line is now drawn against said edge 23, the distance between said lines,

presuming the same thickness of the lines and inclination of the pencil for both lines, will be equal to said clearance. Thus, if the above process of moving the triangle while holding the center piece, and moving'the center piece while holding the triangle, is continued, the edge 23 will be spaced in steps for drawing section lines with the spacing pitch or distance between the lines equal to the clearance with which the piece fits into the central opening, as explained, said clearance being measured at the corner adjacent the edge 23a.

If the triangle and the center piece are turned as a unit from the position shown in Fig. 1 for 90 clockwise to make the edge 21, instead of the edge 2.2, to bear against the straight edge of the T-square, the edge 23 will become disposed for drawing section at lines at 135 to "the base line, another commonly used inclination of the ings or patent drawings, in industrial drafting much coarserpitches are necessary, and therefore the four pitches in a section lining device intended for-industrial drafting would have to be diflerent than the four pitches required for some other types of drafting or for small drawings. In other words, a four-pitch section lining device would have to be made with several models of center pieces which is undesirable.

The centerpiece of the section lining device embodying the present invention is so constructed that it gives up to twelve spacing pitches with a single center piece, attaining the above result without adding any extra parts or mechanisms to the center piece.

From an examination of Fig. 12 it can beapprcciated that the length and the width of the quadrangle for a four-pitch center piece may vary within a rather wide range and still permit to lay out a center piece of any practicable four pitches, which may be distributed around the piece in any order. In a twelve-pitch center piece, its length, width and the order of the pitches around the piece, as well as the freedom of the piece to slide along any of the three edges of the central opening become'im portant. l

The center piece of my improved sectionlining device has the above factors so selected and correlatcdas to give twelve pitches in 45- section lines simply by further varying the positions of the center piece in the triangle opening and of the triangle on the T-square, as explained below. By turning the triangle and the center piece as, a unit forthe angle of counter-clockwise from their positions shown in Figs. 1, 4, 5 and .6, ie by placing them into positions similar to the one shown in Fig. 11, an additional pitch for each of the four pitches, or four additional pitches are made available. In such positions, the respective Slanted corner will now slide on the edge 23a instead of the edge 22a, and the new pitches will be thus increased to 1.414 times of those obtainable in positions of Figs. 1, 4, 5, and 6 respectively. a

When the center piece is turned in the opening into the position shown in Fig. 7 there will be produced an additional spacing pitch preferably, the next larger after the pitch 0f Fig. 6 multiplied by 1.414. Inasmuch as more material is removed from the corners '2 and 4than from the corners -1 and 3, when the center piece is turned end-over-end" and is placed into the position shown in Fig t; in'which position it is resting on the corners 2 and 9- 4, it will sit deeper into the 90 angleof the central opening. Therefore one more spacing pitch is thus produced in such a position. The difference between the pitches of positions of Figs. 7 and 8 depends onthe differences between the numberof spaces removed from the two pairs of corners and is equal to 1/1.4.14 of .707 spaces per each space of difference. In the present instance the total of 4 spaces is removed fromthe corners land 3, while the .total of 6Yspaces is removed-from the corners 2 and 4, giving difference of. 2 spaces. Therefore the difference between these two pitcheswill be equal to .707 multiplied by 2, or 1.414 spaces. .It can be appreciated, that if greater difference between-these two pitches is desired, it may be attained by removing one and two spaces, respectively, from the two upper comers of the center piece, see Fig. 12, and 3 and 4 spaces from the two lower corners thereof. This will give .the difference of 2.828 spaces betweenthese'two pitches. Removing 1 and 4 spaces from the upper corners and 2 and 3 spaces from the lower corners, will produce no difierence, between these pitches, and therefore is undesirable.

Ten spacing pitches being so established, two additional pitches become available by placingpthe triangle and the center pieces into the positions shown in Figs, 9 and 10. The pitch of Fig. 9 will be equalto 1.414 times the pitch of Fig. 7, and the pitch of Fig. 10 will be equal to 1.414 times the pitch of Fig. 8. Thus two more spacing pitches are obtainable, bringing the total number: of

spacing pitches obtainable with the device to twelve.

Twelve spacing. pitches are entirely sufficient. for, the requirements of the common practice of section lining for variety of drafting work, =and,'in fact, I have found that adding still more" spacings would be undesirable as being confusing to the draftsman. a i It can now be seen in view of the foregoing that with 1, 2, 3, and 4 of equal spaces being taken olffromthe corners 1, 2, 3 and 4 respectively, and 6 such spaces being selected as the desired pitch for the position of the piece shown in Fig. 7, twelve spacing pitches of the following number ;of spaces will be obtained: 1; 1.414; 2; 2.828; 3; 4.242 4; 5.656; 6', 8.828; 8686; and 12.483. With A of an inchbeing taken as a unit space, the range with the stationary outline, or a piece of transparent paper with such an outline on it, which I term the movable outline, is next placed on the stationary outline to have both outlines coincide. In this position, the line determining theedge' Sis established on the movable outline by tracing it from the drawn pitch line for this particular edge; This operation will also set the right angle sides of the movable outline to be the lines for the two upper corners .of the center piece, or corners 1 and 3 of the present embodiment. -Next, by placingsaid edges 1 and 3 separately, alongthe edge 23 a at their drawn pitch lines or distances therefrom, with the newly established edge 5 resting in each case on the edge 22a of the opening, the ends'of the center piece are established on the movable outline. .Thereupon'I proceed to the selection of the line for the edge 6, establishing it at such a distance from the edge 5 as to produce the. center piece of such dimensions as to have the working edges of balanced lengths, i.e. of suchrespecti-ve lengths as to enable each edge to have a sufficientlyldng bearing on the edges ofthe central opening of the triangle with the use ofany of the edges and thus preventing rocking of the center piece therein in operation. In the process of this particular step or operation it is important to watch the lines on the stationary outline drawn for the pitches to be obtained with the corners 4 and 2. Having thus selected the line for the edge 6, ,the'lines for edges 4 and 2 are traced on the movableoutline. Thereupon, the centerpiece so outlined is placed on thestationary outline in a position similar to that shown in Fig. 10 and the edges 24 and 25 .of the opening are established at their proper angles and at such distances from the vertices of their respective angles as to clear the center piece while giving the longest practicable edges. It should be remembered in the process of this operation that: the critical position for each of the edges 24and .25,is when the corner 40f the center piece bears on the edge 21o ,or22 a at each ofthe sides, since it is the positions at which the center piece will seat the deepest in the angle of the center opening.

of obtainable pitches will then be from A to slightly over moved from some of the corners, the pitches that come too close together may be made to show more difference, if desired. J

It. should be understood that constructing the center piece by cut and try method is an extremely long, confusing and unsatisfactory procedure. Not only does it take very long time, is tedious, and requires precision models made on a large scale, but it is also extremely confusing. As a result of the use of the cut and try method, some of the spacing pitches, for instance, come out to be substantially duplication of others and, consequently, are of no practical value; in addition, the center piece usually comes out unsatisfactory in length, width, or in other important dimensions. An attempt to remedy the diffi culty by correcting the obvious and similarly minor defect or dimension, changes several spacing pitches at the same time and thus disorganizes the entire construction Which appeared to work perfectly except for the defect in question. An important feature of the present invention is the fact that the center piece is so constructed as to have all of its spacing pitches of desired or predetermined magnitudes. In accordance with the invention, in constructing the center piece, the desired values of the spacing pitches are first set on the basis of the requirements of drafting work and the relationship between the various pitches explained above. Thereupon, the outline of the triangle opening is drawn up on an enlarged scale and a number of parallel lines are drawn within said outline parallel to its edges and at desired'pitch distances therefrom. This forms what I term the stationary outline." A template of transparent material identical in outline By slightly adjusting the amountto be re- Constructed in accordance with the above method for the practically advantageous differences in the spacings obtainabl e,;the center piece comes out in its outline similar to thatofa regular octagon, With relatively small deviations therefrom being due to resulting differences in the length of its sides. Thus, unlike in prior constructions, my improved center piece appears only slightly elongated, its width being greater than one-half of its length. In one actual design, my improved center piece has width slightly in excess of three-fourths of its length. A center piece of such a construction is illustrated in the drawings. It will be also noted that by virtue of such a construction, my improved center piece is received into the opening with its longest side 6 bearing against either of the perpendicular sides of the opening (see Fig. 6), as well as hearing against the hypotenuse side 23a (see Fig. 10).

Marking of the edges of the center piece for their identification may be done in any suitable manner, and preferably the identifying numerals are molded integral with the piece. The numerals themselves may indicate either the actual distance between the section lines produceable with the particular edge, i.e. spacing pitch, or the edges may be marked with a single numeral in numerical order. Some of the designations may be omitted in order not to have too many figures on the center piece, and their location be explained in the instruction pamphlet.

The section lining device so produced is a two piece instrument. I prefer to make the triangle and the piece of two distinct pre-selected colors. This. not only produces a device of pleasing appearance, but makes it easier to locate the small center piece on the board after it has been taken out, and enables identification of particular devices by their owners. Moreover, since most of the countrys engineering and other schools have oflicial school colors of two-color combinations, the triangle and thecenter piece may befrnadeyinoolors of such combine tions,- and thus serve to identify the school of the owner of the device or to express his loyalty ttohis Esch oollf For instance, the triangle may 'be made of lightyelilow attained onthe center piece only by having, say, blue Any other desired? center piece with White markings. color combination may also be used. For general use, I prefer to make the triangle of light transparent green, and the center piece of black color. Such combination is very pleasing and restful for nerves, and the light green color is very restful for the eyes. This also makes'the triangle edge, which must be constantly kept in the sharp focus of the eye of the draftsrnan, more easily distinguishable on the white paper, and thus reduces the eye strain.

There is thus provided an improved drafting instrument whereby the objects of the present invention as listed above and numerous other advantages are attained.

I clairn:

l. A section-lining device-comprising a drafting triangle havin-g a central opening which includes three sides forming, if continued to intersection, a right 45 degree triangle and two sides cutting off the two 45 degree corners of said triangle opening for a substantial distance at 120 degree angles to each of the two perpendicular sides of the opening; and a shuttle piece freely 'placeable into said triangle opening and removable therefrom, said piece comprising a flat body of elongated rectangular shape with all four corners of the rectangle being cut away at 45 degree angles but at fourdifferent distances from the geometric corners of the rectangle to produce an octagonal piece with unequal sides having square edges, thus adapting said pieceto be freely placed into said triangle opening and to be removed therefrom as being free from physical connection with the body of the triangle, with each of said cut-ofi corners of the piece becoming disposed at a respective predetermined and diiferent distance from the hypotenuse edge of the opening when two perpendicular sides of the piece bear against the two perpendicular sides of the triangle in said opening, with said piece being further-adapted. to bear against the two perpendicular sides of the triangle in said opening with two cut-01f corners when either of its longer sides is placed parallel to the hypotenuse side of said opening and with such longer side then becoming disposed at a respective predetermined clearance distance from the hypotenuse side of said opening; with the distance of the two 120 degree sides cut off the corners of the triangle opening from 1he verticesoftthe-45 degree corners thereof being selected 'to be such distances at which theshuttle piece still clears in allbf its operative positions the edges of'the opening formed by saidisides. i g y 2. A section lining device comprising asdrafting triangle having a centralopening including at' least three sides having square edges free of any ridges,with two of said three sides-meeting at a 90 angle and a third sidecextending at 45 angles to said meeting sides, .and a shuttle piece having eight sides and such side relationship to said opening that it may be placed into said opening with either one of its two longest sides bearing against any one of said three sides of the opening and with all edges of said shuttleupiec'e being square and thus adapted to be freely t placeable and removablefrorn said opening in the direction perpendicular to the. general plane of the erasing triangle, said shuttle piece also being, in effect, an elongated rectangular piece having four 90 corners but with each of saidrcorners being cut oil at a 45 angle to. each of the two sides forming the respective corner but at predetermined different distances therefrom to fit into said opening at either of the two predetermined clearances from said third side thereof when placed into said opening with either of the two cut-oft corners of a pair bearing against the'two meeting perpendicular sides of said opening, and with any one of the four predetermined clearance distances from said third side of the opening when it is placed into said opening with two of its perpendicular sides bearing against the two meeting perpendicular sides of'the triangle opening and one of the cut-ofi corners adjacent the third side thereof, and at either of the two clearance distances from either of the two meetingiperpentdicular sides of the opening when it is placed .into said opening with one of its two longest sides bearing on said third side of the opening, with all of said clearance distances being difierent.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Pages 20 and 21 of Notes on Mechanical Drawing, by Rolland S. Wallis, copyright 1922 (33-110). 

